1. Field of the Invention
The present invention relates to a radiation structure for radiating heat generated by an electronic part.
2. Description of the Related Art
Conventionally, many electronic parts including an IC (integrated circuit) are mounted on a printed circuit board for an electronic device. Some of these electronic parts generate heat upon operation. Thus, it is required to effectively radiate heat generated from these electronic parts which generate heat (hereinafter called heating elements).
To this end, in the prior art, as shown in FIG. 3, a through hole 7 is formed at a portion of a printed circuit board 3 on which a heating element 1 is mounted. A radiator 4 is provided with a projection portion 5 having an outer diameter slightly smaller than the diameter of the through hole 7 and having substantially same thickness as that of the printed circuit board 3. Heat radiated from the heating element 1 is radiated through the radiator 4. To be more concrete, the projection portion 5 of the radiator 4 is inserted into the through hole 7 provided at the printed circuit board 3. In this case, silicon grease 2 serving as gelled cementing material is coated on the surface of the heating element 1 facing to the printed circuit board 3 or the upper surface of the projection portion 5 of the radiator so as to homogenize the contacting state of the contacting and opposing surfaces of the heating element 1 and the projection portion 5. The radiator 4 is attached to the printed circuit board 3 through a silicon grease layer 20 which is formed by coating the silicon grease 2 thereby to join the tip end of the projection portion 5 of the radiator 4 to the heating element 1.
According to such a configuration, heat generated from the heating element 1 is radiated in a manner that the heat is transferred to the projection portion 5 of the radiator 4 through the silicon grease layer 20 and further diffused to the entire portion of the radiator.
However, according to the configuration of FIG. 3, at the time of inserting the projection portion 5 of the radiator 4 into the through hole 7 of the printed circuit board 3, it is required to finely adjust an amount of the silicon grease 2 coated on the surface of the heating element 1 facing to the printed circuit board 3 and the upper surface of the projection portion 5 of the radiator 4. Thus, there arises a problem that the attaching procedure is complicated. To be more concrete, if an amount of the silicon grease to be coated is too small, predetermined radiation effect can not be obtained. In contrast, if the amount of the silicon grease to be coated is too much, excessive silicon grease 2 leaks or escapes out of the radiator through the space formed between the printed circuit board 3 and the radiator 4, whereby the leaked grease adheres to a hand of a worker or the parts on the printed circuit board 3 or the like thereby to degrade the workability. Accordingly, it is required to adjust an amount of the silicon grease by taking both the radiation effect and the workability of the attaching procedure into consideration.